Photo of a residential deck construction(C) Daniel FriedmanDeck Ledger Board Installation
Deck Design-Build Online Guide

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The deck ledger, the horizontal framing member that connects the deck to the building forms the starting or reference point for the rest of deck construction. The ledger defines the deck location, width at the building, and height from the ground. The ledger forms the key reference point from which all other deck measurements and plans will be made.

Here we describe how to locate and install the deck ledger board. This article series describes critical safe-construction details for decks and porches, including avoiding deck or porch collapse and unsafe deck stairs and railings.

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Deck Ledger Boards: Connections Between Deck & House

Photograph of a collapsed wood deck.

Attaching the ledger board for a deck

The ledger is a board that is bolted to the house to support one end of the deck joists. It is a bit of a hybrid—part foundation, part framing—and installing it is usually the first construction task in deck building.

With the ledger firmly and properly in place, it will be easier to lay out the rest of the foundation. Procedures for installing a ledger vary, depending upon the type of siding on your house.

Watch out: to avoid a dangerous deck collapse the deck ledger board must be correctly connected to the building structure using proper fasteners that tie to the building structure, and the ledger must be properly flashed to prevent rot and insect damage.

At DECK COLLAPSE Case Study we show what happens when an idiot just tacked the deck ledger to the building through vinyl siding using just some nails.

This article explains deck ledger board installation, connections, & framing.

How to choose the position for the deck ledger board

To keep snow and water away, the finished surface of the deck should be lower than the interior floor of any room leading onto it. To avoid creating a tripping hazard, the deck can be located an inch or less below the interior floor deck surface 4 to 8 inches below the interior floor. This distance will produce a safe, clearly visible step from the deck up to the house. Your local building code may offer more specific guidelines on this issue.

When determining the height at which to install the ledger, you need to take into account both the drop from the interior floor and the thickness of the decking material you plan to install.

How to choose the size of the deck ledger board

As a general rule, you should use the same size of board for the ledger as you plan to use for the joists. You can use a larger board, however, if it allows for a better connection to the house framing. Calculate the length as 3 inches less than the width of the deck framing. This leaves room for the end joists to overlap, and thus hide, the ledger ends. Also, reduce the length of the ledger as needed to allow the decking to overhang the framing.

Some types of siding should be cut away to make room for the ledger. Relatively flat siding, how-ever, can remain intact. Regardless of the type of siding, the strongest ledger connection relies on bolts that run through the ledger and the house sheathing and rim joist, with nuts and washers attached in the basement or crawl space. When access to the other side of the fasteners is not feasible, you can use lag screws instead.

Sometimes it is necessary to use both types of fasteners.

Ledgers should never be merely nailed to the house, and they must always connect to the house framing or foundation— never just the sheathing, which cannot support a deck.

The size and spacing of the bolts should be spelled out in your building code. If they are not, use I/2-inch bolts every 14 inches on decks with joist spans of up to 10 feet; every 10 inches for joist spans of up to 14 feet; and every 8 inches for longer spans. Avoid installing bolts that will interfere with joists and joist hangers. Drill pilot holes as to install carriage bolts or lag screws.

Provide Drainage and Avoid Moisture / Rot / Insect Damage at the Deck Ledger

Figure 4-9: Details of an air-spaced deck ledger (C) J Wiley, S BlissIt is a good idea to leave a space behind the ledger to allow for drainage. This is easily accomplished by placing three or four washers (galvanized or stainless steel) on each bolt.

Alternatively, wood spacers can be cut out of pressure-treated plywood and placed behind the ledger.

As added protection against moisture infiltration, squirt some caulk into the holes before inserting bolts or lag screws.

Watch out: as we discuss below, for virtually every deck installation you will also need to add flashing properly installed to avoid rot, insect damage, leaks into the building, and risk of catastrophic deck collapse when the ledger board fails.

At DECK FLASHING (in our Best Construction Practices article series) we describe two options for deck ledger connection:

1. The deck ledger is bolted directly against the building and flashed to avoid leaks and rot

2. The deck ledger board is connected to the building with a 1/2-inch gap to improve drainage at the building.

Illustration at above left is used with permission and appears in Best Practices Guide to Residential Construction, Chapter Four, Best Construction Guide for Building Decks and Porches.

Connecting a Deck Ledger when the Building Used Nonstandard Building Joists

 If the floors in your house are framed with something other than solid wood, such as wood I-joists or another kind of manufactured joist system, you will probably need to take extra steps to secure the ledger. Discuss your options with the building department or a construction professional.

Removing Siding to Connect the Deck Ledger

If your house has clapboard, beveled wood, metal, or vinyl siding, you will need to remove some siding to accommodate the ledger. Also cut away siding1/2 inches to each side of the ledger to allow for the end joists of the deck.

Plan to remove enough siding so that flashing can be tucked behind the siding above the ledger and overhang the siding below the ledger, Although metal flashing is often installed to cover the top edge of the ledger, a better technique is to extend it below the ledger.

If you will be using self- adhesive membrane instead, prepare for it by removing the entire row of siding above the ledger. After you apply the membrane, reattach the siding.

If your house was built before 1978, there is a good chance that paint on the siding may contain lead. Inhaling lead dust can be harmful, so if you are cutting painted siding of that vintage, wear a HEPA- rated respirator and clean up any paint chips or other debris you create immediately.

Cut the Siding

Carefully mark lines for the cuts on the siding. Make sure to check for level and to allow room for the end joists. Adjust the blade of your circular saw so that it cuts just to the depth of the siding and not into the sheathing underneath. Do not let the blade cut beyond the layout lines. If you are cutting vinyl siding, you can also use a sharp utility knife.

Finish with a Chisel

Use a chisel to finish each cut and make clean corners. You may find it easier to make the vertical cuts with the chisel alone.

Deck Ledger Flashing is Key to Deck Structural Safety & Avoiding Building Leaks

Table of spacing for bolts or screws connecting deck to house (C) J Wiley & Sons, Steven BlissSlide metal flashing beneath the siding. You may need to temporarily remove some siding nails first. Cut the flashing to fit around the door threshold, as shown. Apply caulk to the joint between the threshold and flashing. Details about deck ledger flashing are at these two key additional references:




How to Attach a Deck Ledger Board to a Masonry Wall

Ledgers can also be attached to solid concrete or solid masonry walls. For walls of concrete block, fill the hollow cores with grout; if that is not possible, consult a professional. For solid concrete and grout- filled concrete block, use 1/2-inch galvanized expansion or wedge anchors. For other types of masonry walls, epoxy anchors are best.

Prepare the Wall and Ledger

1.Outline the ledger location on the wall. Drill holes in the ledger for the bolts, taking into account the planned joist locations. Set the ledger against the wall, using 2 x 4s to hold it in place. Mark bolt hole locations on the wall with a nail.

2.Drill the Bolt Holes  Using a hammer drill and masonry bit, drill holes to the depth necessary for the bolts.

3.Attach the Ledger. Remove debris from the drilled holes with a shop vacuum. Prop the ledger back in place and insert an expansion bolt equipped with a washer in each hole. Tighten the bolts with a socket wrench. Apply a bead of silicone caulk to the joint between the wall and the ledger.

Using Epoxy Anchors for Deck Ledger Connections

For a wall that requires epoxy anchors, place a glass vial of epoxy into the hole. Let the epoxy harden, then slip the ledger over the rods, add washers and attach the ledger with nuts. For a wall that requires epoxy anchors, place a glass vial of epoxy into each hole. Quickly insert a threaded rod.

Or for an example of what happens if you foul up the ledger board see DECK COLLAPSE Case Study


Continue reading at DECK LAYOUT or select a topic from the More Reading links shown below.

Or see DECK LEDGER BOARDS - best practices.


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DECK LEDGER BOARD INSTALL at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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